This invention relates generally to photometric analyzers and, more particularly, to the analysis of fluid samples according to their absorption spectra.
It is known in the art that the presence or absence and concentration of a constituent can be determined by exposing a fluid sample alternately to reference and analytical beams, detecting the levels of absorption and computing ratios based on the difference in those levels. The wavelength of the analytical beam is preferentially absorbed by the constituent to be analyzed. The wavelength of the reference beam is not absorbed by the constituent to be analyzed but is absorbed by other constituents in substantially the same proportion as the analytical beam. It is also known that two or more constituents can be analyzed with one photometer by placing a rotating filter wheel between a radiation source and a photodetector. The wheel is opaque except for a plurality of reference and analytical filters and is driven by a synchronous motor. Circuitry is provided for receiving the detected signals and generating outputs related to the differences in absorption by different pairs of filters. Frequently, inaccuracies and inconsistencies related to interferences induced from the power line are noted in the recorded results.